Exceptionally fast carbon–carbon bond reductive elimination from gold(III)

Abstract

Reductive elimination of carbon-carbon (C-C) bonds occurs in numerous metal-catalyzed reactions. This process is well documented for a variety of transition metal complexes. However, C-C bond reductive elimination from a limited number of Au(III) complexes has been shown to be a slow and prohibitive process, generally requiring elevated temperature. Herein, we show that oxidation of a series of mono- and bimetallic Au(I) aryl complexes at low temperature generates observable Au(III) and Au(II) intermediates. We also show that aryl-aryl bond reductive elimination from these oxidized species is not only among the fastest observed for any transition metal, but is also mechanistically distinct from previously studied alkyl-alkyl and aryl-alkyl reductive eliminations from Au(III).

Gold-Catalyzed Oxidative Coupling of Alkynes toward the Synthesis of Cyclic Conjugated Diynes

“…31–35 In this work, we report the gold-catalyzed oxidative coupling of terminal alkynes as an alternative approach to construct cyclic conjugated diynes. The key to this success was the realization of a faster C sp -C sp reductive elimination on gold(III) complexes (comparing with copper-catalyzed Glaser-Hay conditions), 36 which allowed more efficient alkyne coupling under low concentration. Cyclic diynes with size between 13 to 28 atoms were prepared in moderate to good yields, while copper catalysts provided inferior results due to the slow reaction rate under diluted conditions.…”

Gold‐Catalyzed Allylation of Aryl Boronic Acids: Accessing Cross‐Coupling Reactivity with Gold

“…Despite this evidence, attempts to isolate or detect the Au II -Au II intermediate directly have so far proven fruitless, likely due to the rapid rate of reductive elimination. 9 …”

Unique distal size selectivity with a digold catalyst during alkyne homocoupling

“…The reductive elimination from Au(III) complexes to form new C sp 3-X and C sp 2-X bonds (X ¼ heteroatom, C sp 3, C sp 2,y) is a well-known process 13,[29][30][31][32] that has been recently reported to occur very rapidly (even at À 52°C) 33 , faster than in palladium (II). Au(III) intermediates have been isolated and characterized [34][35][36] .…”

“…This lack of precedents for Au(III)-diacetylides might indicate that the reactivity of the alkynes once s-bound to Au(III) is very high, including a potential reductive elimination. It has been proposed that the reductive elimination from a tetracoordinated planar Au(III) complex is favoured respect to other metals 33 since it leaves behind a two-coordinated Au(I) complex stabilized by relativistic effects [39][40][41] . To study the reductive elimination of alkynes from Au(III) and also if the distal size selectivity occurs at this stage, the Au(III) complex PPh 3 AuCl 3 was prepared 42 and the corresponding Au(III) acetylide complex of 1-dodecyne 1b was forced to be formed 43 .…”